Can't create network within subnet of host

[gaaf]

Issue Description

I'm trying to add a network with the same subnet as the host. The containers are supposed to be in a vlan on a (vlan-aware) bridge on the host and within the same subnet as the host.

If I manually edit the network json file, I can get it to work without problem. IMHO the podman network create command should not fail as the (edited) configuration clearly works correctly.

Steps to reproduce the issue

Steps to reproduce the issue

podman network create --interface-name br -o vlan=5 --ipam-driver 'host-local' -o mode=unmanaged --gateway 172.16.1.1 --subnet=172.16.1.0/24 br5

Describe the results you received

Error: subnet 172.16.1.0/24 is already used on the host or by another config

Describe the results you expected

Network creates with the specified subnet and gateway.

podman info output

host:
  arch: amd64
  buildahVersion: 1.39.3
  cgroupControllers:
  - cpuset
  - cpu
  - io
  - memory
  - hugetlb
  - pids
  - rdma
  - misc
  cgroupManager: systemd
  cgroupVersion: v2
  conmon:
    package: conmon_2.1.12-4_amd64
    path: /usr/bin/conmon
    version: 'conmon version 2.1.12, commit: unknown'
  cpuUtilization:
    idlePercent: 92.05
    systemPercent: 2.2
    userPercent: 5.75
  cpus: 8
  databaseBackend: boltdb
  distribution:
    codename: trixie
    distribution: debian
    version: unknown
  eventLogger: journald
  freeLocks: 2046
  hostname: podman1
  idMappings:
    gidmap: null
    uidmap: null
  kernel: 6.12.20-amd64
  linkmode: dynamic
  logDriver: journald
  memFree: 21949050880
  memTotal: 33451249664
  networkBackend: netavark
  networkBackendInfo:
    backend: netavark
    dns:
      package: Unknown
    package: netavark_1.14.0-2_amd64
    path: /usr/lib/podman/netavark
    version: netavark 1.14.0
  ociRuntime:
    name: crun
    package: crun_1.21-1_amd64
    path: /usr/bin/crun
    version: |-
      crun version 1.21
      commit: 10269840aa07fb7e6b7e1acff6198692d8ff5c88
      rundir: /run/user/0/crun
      spec: 1.0.0
      +SYSTEMD +SELINUX +APPARMOR +CAP +SECCOMP +EBPF +CRIU +WASM:wasmedge +YAJL
  os: linux
  pasta:
    executable: ""
    package: ""
    version: ""
  remoteSocket:
    exists: true
    path: /run/podman/podman.sock
  rootlessNetworkCmd: pasta
  security:
    apparmorEnabled: false
    capabilities: CAP_CHOWN,CAP_DAC_OVERRIDE,CAP_FOWNER,CAP_FSETID,CAP_KILL,CAP_NET_BIND_SERVICE,CAP_SETFCAP,CAP_SETGID,CAP_SETPCAP,CAP_SETUID,CAP_SYS_CHROOT
    rootless: false
    seccompEnabled: true
    seccompProfilePath: /usr/share/containers/seccomp.json
    selinuxEnabled: false
  serviceIsRemote: false
  slirp4netns:
    executable: /usr/bin/slirp4netns
    package: slirp4netns_1.2.1-1+b1_amd64
    version: |-
      slirp4netns version 1.2.1
      commit: 09e31e92fa3d2a1d3ca261adaeb012c8d75a8194
      libslirp: 4.8.0
      SLIRP_CONFIG_VERSION_MAX: 4
      libseccomp: 2.6.0
  swapFree: 7939854336
  swapTotal: 8589930496
  uptime: 0h 51m 0.00s
  variant: ""
plugins:
  authorization: null
  log:
  - k8s-file
  - none
  - passthrough
  - journald
  network:
  - bridge
  - macvlan
  - ipvlan
  volume:
  - local
registries: {}
store:
  configFile: /usr/share/containers/storage.conf
  containerStore:
    number: 2
    paused: 0
    running: 2
    stopped: 0
  graphDriverName: overlay
  graphOptions:
    overlay.mountopt: nodev
  graphRoot: /var/lib/containers/storage
  graphRootAllocated: 201786920960
  graphRootUsed: 154039660544
  graphStatus:
    Backing Filesystem: extfs
    Native Overlay Diff: "true"
    Supports d_type: "true"
    Supports shifting: "true"
    Supports volatile: "true"
    Using metacopy: "false"
  imageCopyTmpDir: /var/tmp
  imageStore:
    number: 6
  runRoot: /var/run/containers/storage
  transientStore: false
  volumePath: /var/lib/containers/storage/volumes
version:
  APIVersion: 5.4.1
  BuildOrigin: Debian
  Built: 1742477809
  BuiltTime: Thu Mar 20 14:36:49 2025
  GitCommit: "
  GoVersion: go1.24.1
  Os: linux
  OsArch: linux/amd64
  Version: 5.4.1

Podman in a container

No

Privileged Or Rootless

None

Upstream Latest Release

Yes

Additional environment details

No response

Additional information

No response

[Luap99]

containers/common#2322 for unmanaged networks but the same applies to the vlan option as well of course

[gaaf]

My use case is unmanaged bridge too. Probably also fails without the vlan option.